1. Field of the Invention
The present invention relates to a keyboard, and more particularly to a wireless keyboard used as an input device for a personal computer (hereinafter, referred to as a PC), a workstation or a word processor.
2. Description of the Related Art
Keyboards are most commonly used as devices for inputting characters, numerals and symbols to electronic devices, particularly to information-processing devices such as PCs hereinafter, referred to as a PC main body for convenience).
While such keyboards are generally connected to PC main bodies via cables, various peripherals including keyboards and pointing devices such as mice are also connected to the PC main bodies, so that cables for connecting them are often complicated, causing troubles for deskwork frequently.
Therefore, recently, peripherals connected to the PC main bodies have become wireless (cableless). Among them, since keyboards need to be connected to the PC main bodies in most cases, it is particularly effective to use wireless keyboards.
A keyboard in which wireless transmission is performed is called a wireless keyboard, which is different from a common keyboard in which a transmitting section for a keyboard output signal (in the case of one-way transmission from the keyboard to the PC main body) and antenna wire are added thereto.
Here, while the antenna wire is absolutely necessary to radiate the keyboard output signal from the transmitting section into the air, an antenna wire of a wireless keyboard is disposed in a keyboard casing, as shown in FIG. 8.
In other words, an antenna wire 22 is housed in a keyboard casing 21 and is arranged beyond the keyboard and in the vicinity of a location at which function keys and the like (not shown) are linearly arranged, in such a way that both ends thereof are connected to an output end of a transmitting section 23 and the center thereof is routed in the form of a loop along the keyboard layout, that is, in the longitudinal direction (horizontal direction in the drawing). An area 24 indicated by a two-dot chain line in FIG. 8 denotes a keyboard layout area.
Such an arrangement of the antenna wire 22 is adopted for the following reason. The keyboard consumes a large amount of electric power unlike a pointing device (not shown) such as a mouse. Thus, it is necessary to decrease the power consumption as much as possible for performing wireless transmission, in other words, for achieving the battery power operation.
Accordingly, a low-loss antenna is required. In order to radiate radio waves from the antenna with low loss, it is necessary to perform antenna matching, for example, to set the length of the antenna to an efficiently resonating wavelength or to insert a shorter circuit to further reduce the length.
Actually, the antenna wire 22 is routed in the form of a loop along the longitudinal direction of the keyboard casing 21 so that a maximum length of the antenna can be determined in the keyboard casing 21, as shown in FIG. 8.
In the conventional wireless keyboard, however, routing of the antenna wire 22 is troublesome. Particularly, when an electrically conductive wire with a coating of insulation such as a vinyl resin is used, kinking or curling of the coating occurs in the loop, thus hindering positioning thereof, which is troublesome.
This also means that even if the loop of the antenna wire 22 is positioned with a proper spacing w, it may become deformed or moved to decrease or partly eliminate the spacing w due to impacts to the keyboard casing 21.
Accordingly, it has been necessary to save the time and trouble of routing the antenna wire and to maintain the spacing w.